The present invention refers generally to a ballast bed rehabilitation machine, and more particularly to a machine for withdrawing bulk material, in particular ballast, from a track, having a vertically adjustable bulk material clearing device which is connected to a machine frame and includes a rotatable, endless scraper chain positioned between rails of the track immediately above the track, and a conveyor having a receiving end associated to the bulk material clearing device and extending in a longitudinal direction of the machine frame.
U.S. Pat. No. 5,513,452 describes a ballast bed rehabilitation machine of this type, with the bulk material clearing device being mounted on a leading machine, as viewed in the operating direction. Trailing the leading machine is a ballast bed cleaning machine which is equipped with an excavating chain guided around the track for taking up dirty ballast, and with a conveyor for transport of excavated ballast to a screening unit. The bulk material clearing device is used to take up new ballast which has been temporarily stored between track rails on the track. After being taken up, the new ballast is transported by a trailing conveyor via the transverse chain course which extends underneath the track, and is discharged to the exposed subgrade. In addition, dirty ballast cleaned by the screening unit is deposited on the subgrade. This type of rehabilitation machine affords the possibility to simplify the overall transport logistics in conjunction with a temporary storage of new ballast on the track to complement the deposit of cleaned ballast, if necessary.
U.S. Pat. No. 5,090,483 discloses a mobile track-bound installation combining two cleaning machines arranged successively in an operating direction. The leading cleaning machine includes two excavating chains revolving in the longitudinal direction and spaced from one another transversely to the longitudinal direction for removing dirty ballast from the shoulder area of the track. After being cleaned in a trailing screening unit, cleaned ballast is discharged between the rails of the track and temporarily stored. The trailing cleaning machine includes an endless ballast excavating chain which is guided around the track and is formed with a transverse chain course extending underneath the track for excavating ballast. Positioned above the transverse chain course immediately above the ties is a bridge which is preceded by a rotatable sweeping broom to slightly raise the temporarily stored cleaned ballast from the ties and to transfer it onto the bridge. The bridge is formed substantially by a conveyor belt extending in track direction and discharging the cleaned ballast portion in the continuously advancing excavated ballast bed gap onto the exposed subgrade immediately behind the transverse excavating chain course. Such a mobile installation permits a significant increase of the cleaning performance by using a total of three excavating chains and two screening units.